Watts RBFF 1/2" Residential Boiler Fill Fitting 386466 One-piece construction, eliminating up to 11 threaded joints Unique 3-way ball valve for isolation of water pressure regulator and expansion tank from system pressure Drain port with integral ball valve for unloading pressure from waterside of expansion tank diaphragm for air charge servicing and maintenance. Drain port can also be used for a variety of system draining and filling operations. 0 to 30psi (0 to 87kPa) pressure gauge for convenient system pressure reference